Belt wear is perhaps more due to environment. Salt, Engine fluids, Weather, driving habits and Bad pulleys will cause premature wear. I've seen belts on cars with 100K miles that look fine, then cars with 50K miles and they are shredded.

With that being said belt inspection should be done at every oil change along with other fluids and wear items.

Well after putting in the Stock RSB, driving 80 miles, there's no issues even after hitting a few corners and bumps that would normally cause the noise.

My thoughts are one of two things.1) The Hotchkis RSB wasn't Torqued down enough. 2) The rear control arm bushings are going bad and the combination with the stiffer RSB it's pushing the struts around.

Considering this is a 12-13 y/o car with 160K+ miles with performance parts it will expose problems. I believe #2 is my best guess but #1 is easy and cheap to confirm. However need to wait for the heat index to drop 20F before attempting either.